U.S. patent number 3,875,288 [Application Number 05/389,118] was granted by the patent office on 1975-04-01 for production of synthetic silicate minerals.
This patent grant is currently assigned to NL Industries, Inc.. Invention is credited to H. Michael Blankenship, William T. Granquist, George W. Hoffman.
United States Patent |
3,875,288 |
Hoffman , et al. |
April 1, 1975 |
Production of synthetic silicate minerals
Abstract
Mixed layer 2:1 phyllosilicates of the general type disclosed in
Granquist U.S. Pat. No. 3,252,757 are produced starting with 1:1
clay minerals such as calcined kaolinite and calcined halloysite.
The process provides economies of time as well as of material and
equipment costs. A variant using a pelletized intermediate is
especially advantageous.
Inventors: |
Hoffman; George W. (Houston,
TX), Blankenship; H. Michael (Houston, TX), Granquist;
William T. (Houston, TX) |
Assignee: |
NL Industries, Inc. (New York,
NY)
|
Family
ID: |
23536892 |
Appl.
No.: |
05/389,118 |
Filed: |
August 17, 1973 |
Current U.S.
Class: |
423/118.1;
423/328.2 |
Current CPC
Class: |
C01B
33/26 (20130101); B01J 21/16 (20130101); C01B
33/40 (20130101); C09K 8/05 (20130101); C01B
33/46 (20130101); C01B 33/42 (20130101) |
Current International
Class: |
C09K
8/05 (20060101); B01J 21/00 (20060101); B01J
21/16 (20060101); C09K 8/02 (20060101); C01f
007/00 (); C01b 033/00 () |
Field of
Search: |
;423/118,328,329 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Rosenberg; P. D.
Attorney, Agent or Firm: Larsen; Delmar H. House; Roy F.
Lehman; Robert L.
Claims
Having described the invention, we claim:
1. The process of producing a 2:1 layer-type clay-like mineral
product having the empirical formula:
nSiO.sub.2 :Al.sub.2 O.sub.3 :mAB:xH.sub.2 O
where the layer lattices comprise said silica, said alumina, and
said B, and where
n is from 1.7 to 3.0,
m is from 0.2 to 0.6,
A is one equivalent of an exchangeable cation chosen from the group
consisting of ammonium, sodium, calcium, hydrogen, and mixtures
thereof, and is external to the lattice,
B is chosen from the group of anions which consists of F.sup.-,
OH.sup.-, 1/2 O.sub.2 .sup.-.sup.-, and mixtures thereof, and is
internal in the lattice, and
x is from 2.0 to 3.5 at 50 percent relative humidity, said mineral
being characterized by a d.sub.001 spacing at said humidity within
the range which extends from a lower limit of about 12.0 A. when A
is monovalent, to about 14.7 A. when A is divalent, and to a value
intermediate between 12.0 A. and 14.7 A. when A includes both
monovalent and divalent cations
which comprises the steps of forming a reaction mixture by bringing
together a 1:1 clay chosen from the group consisting of calcined
kaolinite, calcined halloysite, acid-washed calcined kaolinite,
acid-washed calcined halloysite, and mixtures thereof; a cation or
mixture of cations chosen from the group consisting of said A,
together with an equivalent amount of an anion chosen from the
group consisting of hydroxyl and fluoride and mixtures thereof; and
water; the relative quantities of said reaction mixture components
being selected so as to give a molar ratio of SiO.sub.2 /Al.sub.2
O.sub.3 of between about 1.9 and 3.2; of F.sup.-/SiO.sub.2 of
between about 0.02 and 0.3; and of NH.sub.4 .sup.+/Al.sub.2 O.sub.3
of between about 0.1 and 2.0; and so as to give a pH of between
about 4.5 and 11.5 and a solids/water weight ratio of between about
0.08 to about 0.6; and thereafter heating said reaction mixture
under hermetically sealed conditions to a temperature within the
range of about 275.degree. C. to about 320.degree. C. and
maintaining said mixture within said range for a period of time
long enough for said mineral product to form; and thereafter
allowing said mineral product to cool and recovering said mineral
product.
2. The process in accordance with claim 1 wherein said A consists
of NH.sub.4 .sup.+ or NH.sub.4 .sup.+ and H.sup.+ and said B
consists of OH.sup.- and F.sup.-.
3. The process in accordance with claim 1 wherein said reaction
mixture additionally contains a reactive silica in an amount such
that said SiO.sub.2 /Al.sub.2 O.sub.3 ratio does not exceed the
upper limit recited for said reaction mixture.
4. The process in accordance with claim 3 in which said reactive
silica is chosen from the class consisting of polysilicic acid,
fumed silica, diatomite, tripoli, and mixtures thereof.
5. The process in accordance with claim 1 wherein said 1:1 clay and
at least portions each of said cations and anions and water are
first formed into pellets, dried, and calcined at from about
600.degree. to about 700.degree. C., cooled, and thereafter admixed
with the remainder of said anions and cations and water so as to
complete the reaction mixture which is then heated under
hermetically sealed conditions as recited in claim 1 so as to form
said mineral product.
6. The process in accordance with claim 5 in which a minor
proportion of said mineral product from a previous run is admixed
with said clay and said portions of cations and anions and water so
as to act as a binding aid for said pellets.
7. The process in accordance with claim 5 wherein said pellets
additionally contain a reactive silica in an amount such that said
SiO.sub.2 /Al.sub.2 O.sub.3 ratio does not exceed the upper limit
recited for said reaction mixture.
8. The process in accordance with claim 7 in which said reactive
silica is chosen from the class consisting of polysilicic acid,
fumed silica, diatomite, tripoli, and mixtures thereof.
9. The process in accordance with claim 4 in which said A consists
of NH.sub.4 .sup.+ or NH.sub.4 .sup.+ and H.sup.+ and said B
consists of OH.sup.- and F.sup.-.
10. The process in accordance with claim 5 wherein said A consists
of NH.sub.4 .sup.+ or NH.sub.4 .sup.+ and H.sup.+ and said B
consists of OH.sup.- and F.sup.-.
11. The process in accordance with claim 7 in which said A consists
of NH.sub.4 .sup.+ or NH.sub.4 .sup.+ and H.sup.+ and said B
consists of OH.sup.- and F.sup.-.
Description
This invention relates to the hydrothermal synthesis of 2:1
layer-type clay-like minerals of the general type taught in
Granquist U.S. Pat. No. 3,252,757, and more particularly to
improved procedures and a wider range of products within that
category.
The aforesaid U.S. Pat. No. 3,252,757, the disclosure of which is
hereby incorporated herein by reference, teaches a novel
mixed-layer aluminosilicate mineral having manifold utility. The
general procedure set forth therein comprises the formation of a
reaction mixture including silica in reasonably pure form; alumina,
again in relatively pure form; water; and various cations such as
sodium, ammonium, and the like; and various anions, such as
hydroxyl and fluoride. The reaction mixture is hermetically sealed,
as by putting into a pressure vessel such as an autoclave, and is
then heated say to 300.degree. C., and maintained there for a
number of hours until the mineral product has formed. The minerals
thus synthesized have such diverse utility as hydrocarbon cracking
catalysts, oil well drilling mud components, as bases for
organophilic clay greases, and others.
The use of alumina produced by a chemical route as taught in the
aforesaid Granquist patent represents a certain drain on world
energy resources, albeit a small one, considering the metallurgy of
bauxite. Further, the not inconsiderable duration of the high
temperature processing step in this procedure not only consumes
energy but raises production costs generally because of the lesser
throughput possible with a given installation of inherently
expensive equipment.
An object of the present invention is to provide a method of
producing clay-like minerals of the type described with enhanced
economy both in processing time and in raw material cost; and with
a wider range of products.
Other objects of the invention will appear as the description
thereof proceeds.
Generally speaking, and in accordance with illustrative embodiments
of our invention, we produce a 2:1 layer-type clay-like mineral
product having the empirical formula:
nSiO.sub.2 :Al.sub.2 O.sub.3 :mAB:xH.sub.2 O
where the layer lattices comprise silica, alumina, and B, and
where
n is from 1.7 to 3.0,
m is from 0.2 to 0.6,
A is one equivalent of an exchangeable cation chosen from the group
consisting of ammonium, sodium, calcium, hydrogen, and mixtures
thereof, and is external to the lattice,
B is chosen from the group of anions which consists of F.sup.-,
OH.sup.-, 1/2 O.sub.2 .sup.-.sup.-, and mixtures thereof, and is
internal in the lattice, and
x is from 2.0 to 3.5 at 50 percent relative humidity, said mineral
being characterized by a d.sub.001 spacing at said humidity within
the range which extends from a lower limit of about 10.4 A. to an
upper limit of about 12.0 A. when A is monovalent, to about 14.7 A.
when A is divalent, and to a value intermediate between 12.0 A. and
14.7 A. when A includes both monovalent and divalent cations
by first forming a reaction mixture by bringing together a 1:1 clay
chosen from the group consisting of calcined kaolinite, calcined
halloysite, acid-washed calcined kaolinite, acid-washed calcined
halloysite, and mixtures thereof; a cation or mixture of cations
chosen from A above, that is, ammonium, sodium, calcium, hydrogen,
and mixtures thereof, in combination with an equivalent amount of
an anion which may be hydroxyl or fluoride or mixtures thereof; and
water.
The relative quantities of the several reaction mixture components
are selected so as to give a molar ratio of silica to alumina,
i.e., SiO.sub.2 /Al.sub.2 O.sub.3, of between about 1.9 and 3.2; of
fluoride ion to silica, i.e., F.sup.-/SiO.sub.2, of between about
0.02 and 0.3; and of ammonium ion to alumina, i.e., NH.sub.4
.sup.+/Al.sub.2 O.sub.3, of between about 0.1 and 2.0; and so as to
give a pH of between about 4.5 and 11.5; and a solids/water weight
ratio of between about 0.08 and about 0.6, i.e., from about 8
percent to about 60 percent solids.
The reaction mixture having been formed, it is then placed in a
pressure vessel if indeed not already therein, which is then
hermetically sealed and heated to a temperature within the range of
about 275.degree. C. to about 320.degree. C., about 300.degree. C.
being generally preferred. This temperature is maintained until the
2:1 layer-type clay-like mineral product has formed. As will be
seen from the examples which follow, typical times are of the order
of three hours for batches of a kilogram or so. This may be
compared with typical times set forth in the cited Granquist patent
of about 1 to 2 days. We have found that in general as the size of
the equipment and batch increases, the processing times decrease.
Thus, in lots of the order of a ton or so, the Granquist product
may often be made in as short a time as 4 or 5 hours; and for the
same size batch the present invention permits a processing time as
short as 1 hour.
The product having been formed as described, the vessel and
contents are allowed to cool until the vessel may be safely opened,
and the product is recovered. Any after treatment naturally depends
upon the use to be made of the product. Simple draining of excess
liquid with or without drying may be adequate. Or, the solids may
be washed to any desired degree of freedom from excess salts, and
may be base-exchanged with any desired cation or mixture of
cations, and ultimately dried and ground if desired.
The product thus produced in accordance with the invention has the
characteristics described for the product of Granquist U.S. Pat.
No. 3,252,757, and discussed therein in coonsiderable detail. In
particular, quite remarkably the product upon x-ray diffraction no
longer exhibits any content of the starting 1:1 clay, but shows
itself to be comprised of the randomly alternating mixture of
interstratified mica-like and montmorillonite-like layers, both of
which are 2:1 type phyllosilicates. This terminology is well
understood by those skilled in the art. Reference may be made to
the text by Ralph Grim: Clay Mineralogy, Ed. 2, New York 1968, and
in particular chapters 3, on nomenclature, and 4, on structure,
which are hereby incorporated herein by reference.
An especial advantage of the present invention is that it permits
the production of the Granquist-type mineral product with a wider
range of silica-to-alumina ratios than originally disclosed. Thus,
good syntheses may be made at SiO.sub.2 /Al.sub.2 O.sub.3 ratios of
as small as 1.7. [It may be noted that the product in accordance
with the invention generally has an SiO.sub.2 /Al.sub.2 O.sub.3
ratio about 0.2 to 0.3 less than that of the reaction mixture.]
When this is desired, a kaolinite of suitably low silica/alumina
ratio may be selected, since there is some variation in the natural
clay. Alternatively, most halloysites have lower ratios than most
kaolinites.
In the event that higher ratios are desired, reactive silica is
included in the reaction mixture. This may be polysilicic acid,
produced for example in accordance with Hoffman U.S. Pat. No.
3,649,556; or a fumed silica, several of which are commercially
available and which are characterized by extremely fine particle
size, made for example by the silicon monoxide or the silicon
tetrachloride route as described in the book by Ralph Iler: The
Colloid Chemistry of Silica and Silicates, Ithaca 1955, on pages
168-9 and 172-3 thereof; or diatomite; or silica-rich tripoli.
These are all described in Chapter VI of the book by Iler just
cited, which is hereby incorporated herein by reference. The
quantity of reactive silica admixed may be relatively small or
great, but of course should not be so great as to exceed the
silica/alumina ratio for the reaction mixture already specified
herein.
Alternatively, the calcined kaolinite or calcined halloysite may be
acid-washed, which selectively removes alumina by dissolution,
leaving a usable structure with a higher silica/alumina ratio than
the starting clay. Any strong acid may be used, such as sulfuric or
hydrochloric, followed by water-washing to remove the residual acid
and dissolved alumina. In general it is more practical and more
economical to add reactive silica.
As already stated, the kaolinite or halloysite or the mixture of
both is calcined before use in accordance with the invention.
Calcination is carried out within the range 600.degree. to
700.degree. C., preferably about 650.degree. C. The time is not
critical, a half-hour or hour sufficing at the preferred
temperature. Such calcining fundamentally changes the x-ray
diffraction pattern of these clays. If the 1:1 clay is not calcined
first, but used as mined, then the conversion to the unique 2:1
Granquist-type clay does not take place.
It may be noted that many clay firms will supply kaolinite already
calcined to order, so that this step need not be carried out by the
operator of the inventive procedure.
As will be evident from the examples to be given hereinbelow, the
cation-anion combinations used in the reaction mixture may quite
simply comprise ammonium bifluoride, NH.sub.4 F.HF, also written as
NH.sub.4 HF.sub.2 ; and ammonium hydroxide, NH.sub.4 OH, in
preselected proportions to give the desired ratios. Calcium ion is
conveniently added as calcium oxide, or, if included before
calcining, as calcium carbonate. Sodium may be added as the
hydroxide or the fluoride. In general, we prefer a fluoride/silica
ratio of about 0.1; as this ratio diminishes, the reaction time
tends to be prolonged.
A variation in procedure within the broad scope of the invention
comprises the formation of pellets from all or most of the reaction
mixture; or from all of the 1:1 clay and most of the other
ingredients, with enough water to enable pellets to be readily
formed using any commercial pelletizer, as is commonplace in the
catalyst industry. A suitable size for the pellets is from about
one-eighth to three-sixteenths inch in diameter, although this
range may be exceeded. We have had excellent results at one-eighth
inch. Kaolinites and halloysites from different sources tend to
have different pelletizing characteristics, so that in some cases
it may be desirable to include a binder in the mix fed to the
pelletizer. A minor quantity of the mineral product made in
accordance with the invention in a previous run serves admirably;
10 to 20 percent by weight of the calcined 1:1 clay may be used,
for example. Alternatively, or additionally, some of the reactive
silicas have binding properties and may be included for this
purpose, especially polysilicic acid.
While the pellets so produced may be used forthwith, we prefer and
find best to dry the pellets at about 105.degree. C. to 110.degree.
C. and then calcine them at about 600.degree. C. to 700.degree. C.,
and preferably at about 650.degree. C. Remarkably, even though in
the preferred embodiment the pellets will have been made up with
ammonium bifluoride and ammonium hydroxide as already mentioned, no
additional fluoride ion need be incorporated in the final reaction
mixture in spite of the high temperature of calcining. It appears
that a semi-solid-state reaction occurs within the pellets during
the drying and calcining, so that when the final conversion to the
2:1 phyllosilicate product is made in the autoclave, the conversion
time is shortened even more so. The calcination of the pellets has
the further advantage that they tend to retain their shape during
the autoclaving, thus permitting ready access of the chemical
solution surrounding them.
Some examples of the inventive procedure will now be given.
EXAMPLE 1
Five hundred grams of commercially calcined kaolinite were agitated
with 1645 grams of water in a mixer, and 13.3 gm NH.sub.4 HF.sub.2
and 62.3 gm NH.sub.4 OH were added and well-mixed. The reaction
mixture thus formed was placed in a one-gallon laboratory autoclave
provided with a stirring mechanism and heated at 300.degree. C. for
3 hours with agitation. The vessel was cooled to room temperature,
the mineral product removed, sheared with a high-speed blender,
dried at 105.degree. C., and ground.
In this run, the SiO.sub.2 /Al.sub.2 O.sub.3 ratio of the feed was
2.0, and that of the product was 1.93. The NH.sub.4 .sup.+/Al.sub.2
O.sub.3 ratio of the feed was 0.565, and the percent solids was 25.
The F.sup.-/SiO.sub.2 ratio of the feed was 0.1.
EXAMPLE 2
To 565 gms water there were added 1286 gms of a solution of
polysilicic acid containing 4.2 percent by weight of SiO.sub.2. To
this, 500 gm of calcined kaolinite were added, followed by 16.0 gm
NH.sub.4 HF.sub.2 and 59.6 gm NH.sub.4 OH. This was well mixed, and
loaded into an autoclave as in Example 1 above and given the same
treatment for the same time. The SiO.sub.2 /Al.sub.2 O.sub.3 ratio
of the feed was 2.4, and of the mineral product 2.20. The other
ratios and percent solids were as given for Example 1.
EXAMPLE 3
This illustrates a second method of raising the SiO.sub.2 /Al.sub.2
O.sub.3 ratio of the feed and thus of the product, Example 2 having
shown the reactive silica technique. Six hundred gms of calcined
kaolinite were mixed with 1400 gm of water and 144 gm of
66.degree.Be. sulfuric acid, heated to about 88.degree. C., and
maintained at that temperature for 4 hours, with agitation. The
slurry was then cooled to room temperature, filtered, and washed
until free of sulfate ion. It was dried at 105.degree. C. and
ground to pass 200 mesh. It then had an SiO.sub.2 /Al.sub.2 O.sub.3
ratio of 2.3.
The acid-treated kaolinite was then mixed with water, 225 gms of
the clay and 2126 gms of water, to which was added 6.42 gm NH.sub.4
HF.sub.2 and 24.2 gm NH.sub.4 OH. This was then mixed well and
placed into a 1-gallon autoclave as in the previous examples and
maintained at 300.degree. C. for 3 hours with agitation. It was
then cooled and recovered as in Example 1. The SiO.sub.2 /Al.sub.2
O.sub.3 ratio of the feed was 2.3, that of the product not having
been determined. The F.sup.-/SiO.sub.2 ratio of the feed was 0.1,
the NH.sub.4 .sup.+/Al.sub.2 O.sub.3 ratio 0.550, the pH 9.2, and
the solids 10 percent. The product had a pH of 8.7.
EXAMPLE 4
This illustrates the inventive procedure using a pelletized
intermediate. Fifteen lbs. of calcined kaolinite and 0.6 lb.
NH.sub.4 HF.sub.2 were dry blended together, and then admixed with
1.28 lb. NH.sub.4 OH and a slurry of 8.0 lbs. water and 2.55 lbs.
of the Granquist-type mineral product already at hand, and
substantially like the product of Example 1. This mix was of
extrudable consistency, and was formed into one-eighth inch pellets
using a commercial extruder. The pellets were dried at 105.degree.
C. and then calcined at 650.degree. C. for 2 hours.
Into a 1-gallon autoclave were placed 1071 gm of the calcined
pellets together with 2000 gm water and 150 gm NH.sub.4 OH. The
autoclave was brought to 300.degree. C. and maintained there for 3
hours, no agitation being used. The vessel was cooled to room
temperature, and the pellets, which had substantially retained
their shape, were removed and dried at 105.degree. C. The pellets
were ground in a mill to a fine powder, to produce a finished
product. A portion of this milled product was slurried with water
at 20 percent solids and spray dried, to give a product in the form
of microspheres especially adapted to rapid dispersal in various
liquids.
The SiO.sub.2 /Al.sub.2 O.sub.3 ratio of the feed was 2.0, and that
of the product 1.80. The F.sup.-/SiO.sub.2 ratio of the feed was
0.15. The NH.sub.4 .sup.+/Al.sub.2 O.sub.3 ratio of the feed was
0.525.
All of the products of the foregoing examples showed the
characteristics set forth for the Granquist-type mineral in U.S.
Pat. No. 3,252,757. They had a high specific surface as determined
by the Brunauer-Emmett-Teller method, and showed good hydrocarbon
cracking ability when tested in a microcatalytic activity testing
device, using a synthetic crude oil, in the procedure set forth in
Example 10 of U.S. Pat. No. 3,252,757. Results follow:
Table 1 ______________________________________ Example Bulk Density
Percent Conversion Surface Area No. Lbs./Cu.Ft. Cracking Test
M.sup.2 per gm. ______________________________________ 1 20.3 70.2
118 2 18.3 62.9 85 3 n.a. 65.6 81 4 40.1 63.7 107
______________________________________
It will be understood that while we have explained the invention
with the aid of specific examples, nevertheless considerable
variation is possible in choice of raw materials, proportions,
processing conditions, and the like, within the broad scope of the
invention as set forth in the claims which follow.
* * * * *